David Robson: Why fall colors are dull this year

David Robson

Monday

Oct 24, 2011 at 12:01 AMOct 24, 2011 at 12:17 PM

Fall color isn’t as spectacular as it could be, though some maples were a brilliant orange and red. More than likely, the lack of color can be attributed to the lack of moisture throughout summer and fall. What’s great for farmers penalizes those who like to see a kaleidoscope of fall colors.

This year will go down as a weird autumn when it comes to fall colors and leaf drop.

Fall color isn’t as spectacular as it could be, though some maples were a brilliant orange and red. More than likely, the lack of color can be attributed to the lack of moisture throughout summer and fall. What’s great for farmers penalizes those who like to see a kaleidoscope of fall colors.

What’s also unusual is how the trees are coloring. Most trees start hinting at colors in early October. Coupled with cooler weather, which is also missing this year, we get uniform colors with just about all trees showing some changes.

Trees, though, lack a recognized brain and don’t follow what is expected of them. For example, some ginkgo trees have turned yellow and dropped their leaves in the weeklong period of green to yellow to nothing. Those trees stand naked against the sky. Yet, right next to it, another ginkgo is still solid green with no evidence of yellow except at the leaf margins where you might think it’s more a scorch effect because of lack of moisture.

Some sugar maples have been resplendent in their oranges and yellows, while others just turned brown and dropped leaves. Again, inconsistency seems to be the hallmark.

Sassafras trees hit their peak of purples, red, oranges and yellows with more emphasis on the latter two colors. Those leaves are still hanging around.

Persimmons were the ginkgos this year, with the plants turning yellow on one Sunday and dropping all leaves by the following Saturday.

Birch trees started turning yellow and brown, dropping some leaves before they stopped letting them go, although a good rain and wind will probably be more than the tree can resist.

Oaks only seem to be hinting they know it’s October. Most are still green, though the acorn production may be taking all the tree’s efforts. Some trees have skipped the color stage and transformed from green to brown. Still, there should be more of the reds, oranges and golds showing up. Soon.
Hopefully.

Many shrubs are still green, though a few, such as oakleaf hydrangeas, are finally turning. Common lilacs are showing some browning, but no one really looks to them as harbingers of fall colors.

Burning bushes simply aren’t. There might be a hint of cardinal red here and there, but mostly they still resemble what they looked like in August.

When the leaves drop, it’s a good feeling as you can finally do something with the dead foliage. But it’s annoying when you realize that you may have to do something for more than the typical two weekends, unless you let the leaves pile on the ground or blow out of your yard.

There is nothing you can do to make a tree drop its leaves. Cooler weather and rain will do the trick. Genetics does come into play, especially in forested areas where trees are the products of nature or squirrels planting the seed.

Soil type and care can have some effect on the coloration. You shouldn’t find an October Glory turning yellow instead of red, if it were truly an October Glory.

Once a good frost or freeze nips everything, then the green chlorophyll and yellow carotene pigments will break down, leaving behind the red anthocyanin and gold xanthophyll.

More importantly, the leaves will have no reason to remain in place –– the hormonal dynamic will change and abscisic acid comes into play. Nothing moves into or out of the leaf as if an airtight door has come sliding down sealing everything off.

At this point, the leaf shows the last of its pigments, which are the brown tannins. And in all but a few cases, such as pin oaks and shingle oaks, the law of gravity takes over and the leaf floats down.

At this point, your next several weekends become devoted to removing
leaves from your yard, whether by mowing and mulching, raking, bagging, burning –– in some cases, where it’s legal –– blowing or just hoping that they magically disappear overnight.

David Robson is a specialist with University of Illinois Extension.

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